HLASM Language Reference

Positional Parameters
Symbolic parameters have a local scope; that is, the name and value they are
assigned only applies to the macro definition in which they have been declared.
The value of the parameter remains constant throughout the processing of the
containing macro definition during each call of that definition.
Notes:
1. Symbolic parameters must not have multiple definitions or be identical to any
other variable symbols within the given local scope. This applies to the system
variable symbols described in “System Variable Symbols” on page 262, and to
local-scope and global-scope SET symbols described in “SET Symbols” on
page 319.
2. Symbolic parameters should not begin with &SYS because these characters are
used for system variable symbols provided with High Level Assembler.
The two kinds of symbolic parameters are:
Positional parameters
Keyword parameters
Each positional or keyword parameter used in the body of a macro definition must
be declared in the prototype statement.
The following is an example of a macro definition with symbolic parameters.
MACRO
Header
&NAME MOVE &TO,&FROM Prototype
&NAME ST 2,SAVE Model
L 2,&FROM Model
ST 2,&TO Model
L 2,SAVE Model
MEND
Trailer
In the following macro instruction that calls the above macro, the characters HERE,
FIELDA, and FIELDB of the MOVE macro instruction correspond to the symbolic
parameters &NAME, &TO, and &FROM, respectively, of the MOVE prototype statement.
HERE MOVE FIELDA,FIELDB
If the preceding macro instruction were used in a source program, the following
assembler language statements would be generated:
HERE ST 2,SAVE
L
2,FIELDB
ST
2,FIELDA
L
2,SAVE
Positional Parameters
You should use a positional parameter in a macro definition if you want to change
the value of the parameter each time you call the macro definition. This is because
it is easier to supply the value for a positional parameter than for a keyword
parameter. You only have to write the value you want the corresponding argument
to have in the correct position in the operand of the calling macro instruction.
However, if you need a large number of parameters, you should use keyword
parameters. The keywords make it easier to keep track of the individual values you
254 HLASM V1R5 Language Reference